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10 <div class="doc_title">
11 Getting Started with the LLVM System
15 <li><a href="#overview">Overview</a>
16 <li><a href="#quickstart">Getting Started Quickly (A Summary)</a>
17 <li><a href="#requirements">Requirements</a>
19 <li><a href="#hardware">Hardware</a>
20 <li><a href="#software">Software</a>
21 <li><a href="#brokengcc">Broken versions of GCC</a>
24 <li><a href="#starting">Getting Started with LLVM</a>
26 <li><a href="#terminology">Terminology and Notation</a>
27 <li><a href="#environment">Setting Up Your Environment</a>
28 <li><a href="#unpack">Unpacking the LLVM Archives</a>
29 <li><a href="#checkout">Checkout LLVM from CVS</a>
30 <li><a href="#installcf">Install the GCC Front End</a>
31 <li><a href="#config">Local LLVM Configuration</a>
32 <li><a href="#compile">Compiling the LLVM Suite Source Code</a>
33 <li><a href="#objfiles">The Location of LLVM Object Files</a>
34 <li><a href="#optionalconfig">Optional Configuration Items</a>
37 <li><a href="#layout">Program layout</a>
39 <li><a href="#cvsdir"><tt>CVS</tt> directories</a>
40 <li><a href="#include"><tt>llvm/include</tt></a>
41 <li><a href="#lib"><tt>llvm/lib</tt></a>
42 <li><a href="#runtime"><tt>llvm/runtime</tt></a>
43 <li><a href="#test"><tt>llvm/test</tt></a>
44 <li><a href="#tools"><tt>llvm/tools</tt></a>
45 <li><a href="#utils"><tt>llvm/utils</tt></a>
48 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
49 <li><a href="#problems">Common Problems</a>
50 <li><a href="#links">Links</a>
53 <div class="doc_author">
55 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
56 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
57 <a href="http://misha.brukman.net">Misha Brukman</a>,
58 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
59 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.
64 <!-- *********************************************************************** -->
65 <div class="doc_section">
66 <a name="overview"><b>Overview</b></a>
68 <!-- *********************************************************************** -->
70 <div class="doc_text">
72 <p>Welcome to LLVM! In order to get started, you first need to know some
73 basic information.</p>
75 <p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
76 contains all of the tools, libraries, and header files needed to use the low
77 level virtual machine. It contains an assembler, disassembler, bytecode
78 analyzer, and bytecode optimizer. It also contains a test suite that can be
79 used to test the LLVM tools and the GCC front end.</p>
81 <p>The second piece is the GCC front end. This component provides a version of
82 GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
83 end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
84 compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
85 from the LLVM suite.</p>
89 <!-- *********************************************************************** -->
90 <div class="doc_section">
91 <a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a>
93 <!-- *********************************************************************** -->
95 <div class="doc_text">
97 <p>Here's the short story for getting up and running quickly with LLVM:</p>
100 <li>Install the GCC front end:
102 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt>
103 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
104 <li><b>Sparc and MacOS X Only:</b><br>
105 <tt>cd cfrontend/<i>platform</i><br>
109 <li>Get the Source Code
111 <li>With the distributed files:
113 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
114 <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
118 <li>With anonymous CVS access (or use a <a href="#mirror">mirror</a>):
120 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
122 :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt></li>
123 <li>Hit the return key when prompted for the password.
124 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm
126 <li><tt>cd llvm</tt></li>
130 <li>Configure the LLVM Build Environment
132 <li>Change directory to where you want to store the LLVM object
133 files and run <tt>configure</tt> to configure the Makefiles and
134 header files for the default platform. Useful options include:
136 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
137 <p>Specify the full pathname of where the LLVM GCC frontend is
139 <li><tt>--enable-spec2000=<i>directory</i></tt>
140 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
141 benchmarks should be available in
142 <tt><i>directory</i></tt>.</p></li>
146 <li>Build the LLVM Suite:
148 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.</li>
149 <li><tt>gmake -k |& tee gnumake.out
150 # this is csh or tcsh syntax</tt></li>
151 <li>If you get an "internal compiler error (ICE)" see <a href="#brokengcc">below</a>.</li>
156 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
157 detailed information on configuring and compiling LLVM. See <a
158 href="#environment">Setting Up Your Environment</a> for tips that simplify
159 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
160 Layout</a> to learn about the layout of the source code tree.</p>
164 <!-- *********************************************************************** -->
165 <div class="doc_section">
166 <a name="requirements"><b>Requirements</b></a>
168 <!-- *********************************************************************** -->
170 <div class="doc_text">
172 <p>Before you begin to use the LLVM system, review the requirements given below.
173 This may save you some trouble by knowing ahead of time what hardware and
174 software you will need.</p>
178 <!-- ======================================================================= -->
179 <div class="doc_subsection">
180 <a name="hardware"><b>Hardware</b></a>
183 <div class="doc_text">
185 <p>LLVM is known to work on the following platforms:</p>
189 <li>Linux on x86 (Pentium and above)
191 <li>Approximately 1.02 GB of Free Disk Space
193 <li>Source code: 45 MB</li>
194 <li>Object code: 956 MB</li>
195 <li>GCC front end: 40 MB</li>
200 <li>Solaris on SparcV9 (Ultrasparc)
202 <li>Approximately 1.75 GB of Free Disk Space
204 <li>Source code: 45 MB</li>
205 <li>Object code: 1.7 GB</li>
206 <li>GCC front end: 50 MB</li>
211 <li>FreeBSD on x86 (Pentium and above)
213 <li>Approximately 935 MB of Free Disk Space
215 <li>Source code: 45 MB</li>
216 <li>Object code: 850 MB</li>
217 <li>GCC front end: 40 MB</li>
222 <li>MacOS X on PowerPC
224 <li>Approximately 1.25 GB of Free Disk Space
226 <li>Source code: 45 MB</li>
227 <li>Object code: 1.2 GB</li>
228 <li>GCC front end: 40 MB</li>
235 <li><div class="doc_warning">No native code generation</div>
236 <li>Approximately 2 GB of Free Disk Space
238 <li>Source code: 92 MB</li>
239 <li>Object code: 2.8 GB</li>
240 <li>GCC front end: 123 MB</li>
247 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
248 guaranteed to do so. If compilation is successful, the LLVM utilities should be
249 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
250 generation should work as well, although the generated native code may not work
251 on your platform.</p>
253 <p>The GCC front end is not very portable at the moment. If you want to get it
254 to work on another platform, you can download a copy of the source and <a
255 href="CFEBuildInstrs.html">try to compile it</a> on your platform.</p>
259 <!-- ======================================================================= -->
260 <div class="doc_subsection">
261 <a name="software"><b>Software</b></a>
264 <div class="doc_text">
266 <p>Compiling LLVM requires that you have several software packages
270 <li><a href="http://gcc.gnu.org">GCC 3.x with C and C++ language
271 support</a> (See <a href="#brokengcc">below</a> for specific version info)</li>
273 <li><a href="http://savannah.gnu.org/projects/make">GNU Make</a></li>
275 <li><a href="http://www.gnu.org/software/flex">Flex</a></li>
277 <li><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></li>
280 <p>There are some additional tools that you may want to have when working with
284 <li><A href="http://www.gnu.org/software/automake">GNU Automake</A></li>
285 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A></li>
286 <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
288 <p>If you want to make changes to the configure scripts, you will need GNU
289 autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4 or
290 higher). You will also need automake. Any old version of
291 automake from 1.4p5 on should work; we only use aclocal from that
294 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest 2.0.3</A></li>
295 <li><A href="http://www.python.org">Python</A>
298 These are needed to use the LLVM test suite. Please note that newer
299 versions of QMTest may not work with the LLVM test suite. QMTest 2.0.3
300 can be retrieved from the QMTest CVS repository using the following
303 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository login</tt>
305 <li>When prompted, use <tt>anoncvs</tt> as the password.
307 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository co -r release-2-0-3 qm</tt>
315 <!-- ======================================================================= -->
316 <div class="doc_subsection">
317 <a name="brokengcc">Broken versions of GCC</a>
320 <div class="doc_text">
322 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
323 bugs in the compiler. In particular, several versions of GCC crash when trying
324 to compile LLVM. We routinely use GCC 3.3.3 and GCC 3.4.0 and have had success
325 with them. Other versions of GCC will probably work as well. GCC versions listed
326 here are known to not work. If you are using one of these versions, please try
327 to upgrade your GCC to something more recent. If you run into a problem with a
328 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
329 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
330 of GCC you are using.
333 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
334 problems in the STL that effectively prevent it from compiling LLVM.
337 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
338 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
339 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
345 <!-- *********************************************************************** -->
346 <div class="doc_section">
347 <a name="starting"><b>Getting Started with LLVM</b></a>
349 <!-- *********************************************************************** -->
351 <div class="doc_text">
353 <p>The remainder of this guide is meant to get you up and running with
354 LLVM and to give you some basic information about the LLVM environment.</p>
356 <p>The later sections of this guide describe the <a
357 href="#layout">general layout</a> of the the LLVM source tree, a <a
358 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
359 href="#links">links</a> to find more information about LLVM or to get
363 <!-- ======================================================================= -->
364 <div class="doc_subsection">
365 <a name="terminology">Terminology and Notation</a>
368 <div class="doc_text">
370 <p>Throughout this manual, the following names are used to denote paths
371 specific to the local system and working environment. <i>These are not
372 environment variables you need to set but just strings used in the rest
373 of this document below</i>. In any of the examples below, simply replace
374 each of these names with the appropriate pathname on your local system.
375 All these paths are absolute:</p>
380 This is the top level directory of the LLVM source tree.
385 This is the top level directory of the LLVM object tree (i.e. the
386 tree where object files and compiled programs will be placed. It
387 can be the same as SRC_ROOT).
392 This is the where the LLVM GCC Front End is installed.
394 For the pre-built GCC front end binaries, the LLVMGCCDIR is
395 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
400 <!-- ======================================================================= -->
401 <div class="doc_subsection">
402 <a name="environment">Setting Up Your Environment</a>
405 <div class="doc_text">
408 In order to compile and use LLVM, you will need to set some environment
409 variables. There are also some shell aliases which you may find useful.
410 You can set these on the command line, or better yet, set them in your
411 <tt>.cshrc</tt> or <tt>.profile</tt>.
414 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
416 This environment variable helps the LLVM GCC front end find bytecode
417 libraries that it will need for compilation.
420 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
421 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
423 This alias allows you to use the LLVM C and C++ front ends without putting
424 them in your <tt>PATH</tt> or typing in their complete pathnames.
429 <!-- ======================================================================= -->
430 <div class="doc_subsection">
431 <a name="unpack">Unpacking the LLVM Archives</a>
434 <div class="doc_text">
437 If you have the LLVM distribution, you will need to unpack it before you
438 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
439 suite and the LLVM GCC front end compiled for your platform. Each
440 file is a TAR archive that is compressed with the gzip program.
443 <p> The files are as follows:
446 <dd>This is the source code to the LLVM suite.
449 <dt>cfrontend-1.2.sparc-sun-solaris2.8.tar.gz
450 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
453 <dt>cfrontend-1.2.i686-redhat-linux-gnu.tar.gz
454 <dd>This is the binary release of the GCC front end for Linux/x86.
457 <dt>cfrontend-1.2.i386-unknown-freebsd5.1.tar.gz
458 <dd>This is the binary release of the GCC front end for FreeBSD/x86.
461 <dt>cfrontend-1.2.powerpc-apple-darwin7.0.0.tar.gz
462 <dd>This is the binary release of the GCC front end for MacOS X/PPC.
467 <!-- ======================================================================= -->
468 <div class="doc_subsection">
469 <a name="checkout">Checkout LLVM from CVS</a>
472 <div class="doc_text">
474 <p>If you have access to our CVS repository, you can get a fresh copy of
475 the entire source code. All you need to do is check it out from CVS as
479 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
480 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
481 <li>Hit the return key when prompted for the password.
482 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
486 <p>This will create an '<tt>llvm</tt>' directory in the current
487 directory and fully populate it with the LLVM source code, Makefiles,
488 test directories, and local copies of documentation files.</p>
490 <p>If you want to get a specific release (as opposed to the most recent
491 revision), you can specify a label. The following releases have the following
495 <li>Release 1.2: <b>RELEASE_12</b></li>
496 <li>Release 1.1: <b>RELEASE_11</b></li>
497 <li>Release 1.0: <b>RELEASE_1</b></li>
500 <p>If you would like to get the GCC front end source code, you can also get it
501 from the CVS repository:</p>
504 cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-gcc
507 <p>Please note that you must follow <a href="CFEBuildInstrs.html">these
508 instructions</a> to successfully build the LLVM C front-end.</p>
512 <!-- ======================================================================= -->
513 <div class="doc_subsubsection">
514 <a name="mirrors">LLVM CVS Mirrors</a>
517 <div class="doc_text">
519 <p>If the main CVS server is overloaded or inaccessible, you can try one of
520 these user-hosted mirrors:</p>
523 <li><a href="http://llvm.x10sys.com/">Mirror hosted by eXtensible Systems
528 <!-- ======================================================================= -->
529 <div class="doc_subsection">
530 <a name="installcf">Install the GCC Front End</a>
533 <div class="doc_text">
535 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
536 GCC front end from the binary distribution. It is used for building the
537 bytecode libraries later used by the GCC front end for linking programs, and its
538 location must be specified when the LLVM suite is configured.</p>
540 <p>To install the GCC front end, do the following:</p>
543 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
544 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
548 <p>If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the
551 <p><tt>cd cfrontend/<i>platform</i><br>
552 ./fixheaders</tt></p>
554 <p>The binary versions of the GCC front end may not suit all of your needs. For
555 example, the binary distribution may include an old version of a system header
556 file, not "fix" a header file that needs to be fixed for GCC, or it may be
557 linked with libraries not available on your system.</p>
559 <p>In cases like these, you may want to try <a
560 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
561 not for the faint of heart, so be forewarned.</p>
565 <!-- ======================================================================= -->
566 <div class="doc_subsection">
567 <a name="config">Local LLVM Configuration</a>
570 <div class="doc_text">
572 <p>Once checked out from the CVS repository, the LLVM suite source code must be
573 configured via the <tt>configure</tt> script. This script sets variables in
574 <tt>llvm/Makefile.config</tt> and <tt>llvm/include/Config/config.h</tt>. It
575 also populates <i>OBJ_ROOT</i> with the Makefiles needed to begin building
578 <p>The following environment variables are used by the <tt>configure</tt>
579 script to configure the build system:</p>
589 <td>Tells <tt>configure</tt> which C compiler to use. By default,
590 <tt>configure</tt> will look for the first GCC C compiler in
591 <tt>PATH</tt>. Use this variable to override
592 <tt>configure</tt>'s default behavior.</td>
597 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
598 <tt>configure</tt> will look for the first GCC C++ compiler in
599 <tt>PATH</tt>. Use this variable to override
600 <tt>configure</tt>'s default behavior.</td>
604 <p>The following options can be used to set or enable LLVM specific options:</p>
607 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
609 Path to the location where the LLVM GCC front end binaries and
610 associated libraries were installed. This must be specified as an
613 <dt><i>--enable-optimized</i>
615 Enables optimized compilation by default (debugging symbols are removed
616 and GCC optimization flags are enabled). The default is to use an
617 unoptimized build (also known as a debug build).
619 <dt><i>--enable-jit</i>
621 Compile the Just In Time (JIT) compiler functionality. This is not
623 on all platforms. The default is dependent on platform, so it is best
624 to explicitly enable it if you want it.
626 <dt><i>--enable-spec2000</i>
627 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
629 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
630 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
631 <tt>directory</tt>, you can tell configure where to find the SPEC2000
632 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
633 uses the default value
634 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
636 <dt><i>--enable-spec95</i>
637 <dt><i>--enable-spec95=<<tt>directory</tt>></i>
639 Enable the use of SPEC95 when testing LLVM. It is similar to the
640 <i>--enable-spec2000</i> option.
642 <dt><i>--enable-povray</i>
643 <dt><i>--enable-povray=<<tt>directory</tt>></i>
645 Enable the use of Povray as an external test. Versions of Povray written
646 in C should work. This option is similar to the <i>--enable-spec2000</i>
650 <p>To configure LLVM, follow these steps:</p>
653 <li>Change directory into the object root directory:
655 <tt>cd <i>OBJ_ROOT</i></tt>
658 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
660 <tt><i>SRC_ROOT</i>/configure</tt>
664 <p>In addition to running <tt>configure</tt>, you must set the
665 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
666 This environment variable is used to locate "system" libraries like
667 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set to
668 the absolute path of the <tt>bytecode-libs</tt> subdirectory of the GCC front
669 end, or <i>LLVMGCCDIR</i>/<tt>bytecode-libs</tt>. For example, one might set
670 <tt>LLVM_LIB_SEARCH_PATH</tt> to
671 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the x86
672 version of the GCC front end on our research machines.</p>
676 <!-- ======================================================================= -->
677 <div class="doc_subsection">
678 <a name="compile">Compiling the LLVM Suite Source Code</a>
681 <div class="doc_text">
683 <p>Once you have configured LLVM, you can build it. There are three types of
689 These builds are the default when one types <tt>gmake</tt> (unless the
690 <tt>--enable-optimized</tt> option was used during configuration). The
691 build system will compile the tools and libraries with debugging
695 <dt>Release (Optimized) Builds
697 These builds are enabled with the <tt>--enable-optimized</tt> option to
698 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
699 <tt>gmake</tt> command line. For these builds, the build system will
700 compile the tools and libraries with GCC optimizations enabled and strip
701 debugging information from the libraries and executables it generates.
706 These builds are for use with profiling. They compile profiling
707 information into the code for use with programs like <tt>gprof</tt>.
708 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
709 on the <tt>gmake</tt> command line.
712 <p>Once you have LLVM configured, you can build it by entering the
713 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
715 <p><tt>gmake</tt></p>
717 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
718 are using a known broken version of GCC to compile LLVM with.</p>
721 If you have multiple processors in your machine, you may wish to use some of
722 the parallel build options provided by GNU Make. For example, you could use the
725 <p><tt>gmake -j2</tt></p>
727 <p>There are several special targets which are useful when working with the LLVM
731 <dt><tt>gmake clean</tt>
733 Removes all files generated by the build. This includes object files,
734 generated C/C++ files, libraries, and executables.
737 <dt><tt>gmake distclean</tt>
739 Removes everything that <tt>gmake clean</tt> does, but also removes
740 files generated by <tt>configure</tt>. It attempts to return the
741 source tree to the original state in which it was shipped.
744 <dt><tt>gmake install</tt>
746 Installs LLVM files into the proper location. For the most part,
747 this does nothing, but it does install bytecode libraries into the
748 GCC front end's bytecode library directory. If you need to update
749 your bytecode libraries, this is the target to use once you've built
754 <p>It is also possible to override default values from <tt>configure</tt> by
755 declaring variables on the command line. The following are some examples:</p>
758 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
760 Perform a Release (Optimized) build.
763 <dt><tt>gmake ENABLE_PROFILING=1</tt>
765 Perform a Profiling build.
768 <dt><tt>gmake VERBOSE=1</tt>
770 Print what <tt>gmake</tt> is doing on standard output.
774 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
775 it and any subdirectories that it contains. Entering any directory inside the
776 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
777 that directory that is out of date.</p>
781 <!-- ======================================================================= -->
782 <div class="doc_subsection">
783 <a name="objfiles">The Location of LLVM Object Files</a>
786 <div class="doc_text">
788 <p>The LLVM build system is capable of sharing a single LLVM source tree among
789 several LLVM builds. Hence, it is possible to build LLVM for several different
790 platforms or configurations using the same source tree.</p>
792 <p>This is accomplished in the typical autoconf manner:</p>
795 <li><p>Change directory to where the LLVM object files should live:</p>
797 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
799 <li><p>Run the <tt>configure</tt> script found in the LLVM source
802 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
805 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
806 named after the build type:</p>
813 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
815 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
823 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
825 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
833 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
835 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
841 <!-- ======================================================================= -->
842 <div class="doc_subsection">
843 <a name="optionalconfig">Optional Configuration Items</a>
846 <div class="doc_text">
849 If you're running on a linux system that supports the "<a
850 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
851 module, and you have root access on the system, you can set your system up to
852 execute LLVM bytecode files directly. To do this, use commands like this (the
853 first command may not be required if you are already using the module):</p>
856 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
857 $ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
858 $ chmod u+x hello.bc (if needed)
863 This allows you to execute LLVM bytecode files directly. Thanks to Jack
864 Cummings for pointing this out!
870 <!-- *********************************************************************** -->
871 <div class="doc_section">
872 <a name="layout"><b>Program Layout</b></a>
874 <!-- *********************************************************************** -->
876 <div class="doc_text">
878 <p>One useful source of information about the LLVM source base is the LLVM <a
879 href="http://www.doxygen.org">doxygen</a> documentation available at <tt><a
880 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
881 The following is a brief introduction to code layout:</p>
885 <!-- ======================================================================= -->
886 <div class="doc_subsection">
887 <a name="cvsdir"><tt>CVS</tt> directories</a>
890 <div class="doc_text">
892 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
893 the most part these can just be ignored.</p>
897 <!-- ======================================================================= -->
898 <div class="doc_subsection">
899 <a name="include"><tt>llvm/include</tt></a>
902 <div class="doc_text">
904 <p>This directory contains public header files exported from the LLVM
905 library. The three main subdirectories of this directory are:</p>
908 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
909 specific header files. This directory also has subdirectories for
910 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
911 <tt>Target</tt>, <tt>Transforms</tt>, etc...</li>
913 <li><tt>llvm/include/Support</tt> - This directory contains generic
914 support libraries that are independent of LLVM, but are used by LLVM.
915 For example, some C++ STL utilities and a Command Line option processing
916 library store their header files here.</li>
918 <li><tt>llvm/include/Config</tt> - This directory contains header files
919 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
920 and C header files. Source code can include these header files which
921 automatically take care of the conditional #includes that the
922 <tt>configure</tt> script generates.</li>
927 <!-- ======================================================================= -->
928 <div class="doc_subsection">
929 <a name="lib"><tt>llvm/lib</tt></a>
932 <div class="doc_text">
934 <p>This directory contains most of the source files of the LLVM system. In LLVM,
935 almost all code exists in libraries, making it very easy to share code among the
936 different <a href="#tools">tools</a>.</p>
939 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
940 source files that implement core classes like Instruction and BasicBlock.
942 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
943 for the LLVM assembly language parser library.
945 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
946 and write LLVM bytecode.
948 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
951 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
952 different program analyses, such as Dominator Information, Call Graphs,
953 Induction Variables, Interval Identification, Natural Loop Identification,
956 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
957 code for the LLVM to LLVM program transformations, such as Aggressive Dead
958 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
959 Invariant Code Motion, Dead Global Elimination, and many others...
961 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
962 describe various target architectures for code generation. For example,
963 the llvm/lib/Target/SparcV9 directory holds the Sparc machine
966 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
967 of the code generator: Instruction Selector, Instruction Scheduling, and
970 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
971 that corresponds to the header files located in
972 <tt>llvm/include/Support/</tt>.
977 <!-- ======================================================================= -->
978 <div class="doc_subsection">
979 <a name="runtime"><tt>llvm/runtime</tt></a>
982 <div class="doc_text">
984 <p>This directory contains libraries which are compiled into LLVM bytecode and
985 used when linking programs with the GCC front end. Most of these libraries are
986 skeleton versions of real libraries; for example, libc is a stripped down
987 version of glibc.</p>
989 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
994 <!-- ======================================================================= -->
995 <div class="doc_subsection">
996 <a name="test"><tt>llvm/test</tt></a>
999 <div class="doc_text">
1001 <p>This directory contains regression tests and source code that is used to test
1002 the LLVM infrastructure.</p>
1006 <!-- ======================================================================= -->
1007 <div class="doc_subsection">
1008 <a name="tools"><tt>llvm/tools</tt></a>
1011 <div class="doc_text">
1013 <p>The <b>tools</b> directory contains the executables built out of the
1014 libraries above, which form the main part of the user interface. You can
1015 always get help for a tool by typing <tt>tool_name --help</tt>. The
1016 following is a brief introduction to the most important tools:</p>
1019 <dt><tt><b>analyze</b></tt> <dd><tt>analyze</tt> is used to run a specific
1020 analysis on an input LLVM bytecode file and print out the results. It is
1021 primarily useful for debugging analyses, or familiarizing yourself with
1022 what an analysis does.<p>
1024 <dt><tt><b>bugpoint</b></tt> <dd><tt>bugpoint</tt> is used to debug
1025 optimization passes or code generation backends by narrowing down the
1026 given test case to the minimum number of passes and/or instructions that
1027 still cause a problem, whether it is a crash or miscompilation. See <a
1028 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1029 on using <tt>bugpoint</tt>.<p>
1031 <dt><tt><b>llvm-ar</b></tt> <dd>The archiver produces an archive containing
1032 the given LLVM bytecode files, optionally with an index for faster
1035 <dt><tt><b>llvm-as</b></tt> <dd>The assembler transforms the human readable
1036 LLVM assembly to LLVM bytecode.<p>
1038 <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
1039 bytecode to human readable LLVM assembly.<p>
1041 <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
1042 links multiple LLVM modules into a single program.<p>
1044 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
1045 can directly execute LLVM bytecode (although very slowly...). In addition
1046 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
1047 specifying <tt>-trace</tt> on the command line). Finally, for
1048 architectures that support it (currently only x86 and Sparc), by default,
1049 <tt>lli</tt> will function as a Just-In-Time compiler (if the
1050 functionality was compiled in), and will execute the code <i>much</i>
1051 faster than the interpreter.<p>
1053 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler, which
1054 translates LLVM bytecode to a SPARC or x86 assembly file, or to C code (with
1055 the -march=c option).<p>
1057 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
1058 that has been retargeted to emit LLVM code as the machine code output. It
1059 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
1060 -o</tt> options that are typically used. The source code for the
1061 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
1062 because it is quite large and not very interesting.<p>
1066 <dt><tt><b>gccas</b></tt> <dd>This tool is invoked by the
1067 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
1068 tool actually assembles LLVM assembly to LLVM bytecode,
1069 performs a variety of optimizations, and outputs LLVM bytecode. Thus
1070 when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
1071 <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
1072 an LLVM bytecode file that can be disassembled or manipulated just like
1073 any other bytecode file). The command line interface to <tt>gccas</tt>
1074 is designed to be as close as possible to the <b>system</b>
1075 `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
1076 modified to interface to a "weird" assembler.<p>
1078 <dt><tt><b>gccld</b></tt> <dd><tt>gccld</tt> links together several LLVM
1079 bytecode files into one bytecode file and does some optimization. It is
1080 the linker invoked by the GCC frontend when multiple .o files need to be
1081 linked together. Like <tt>gccas</tt>, the command line interface of
1082 <tt>gccld</tt> is designed to match the system linker, to aid
1083 interfacing with the GCC frontend.</dl><p>
1086 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
1087 series of LLVM to LLVM transformations (which are specified on the command
1088 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
1089 command is a good way to get a list of the program transformations
1096 <!-- ======================================================================= -->
1097 <div class="doc_subsection">
1098 <a name="utils"><tt>llvm/utils</tt></a>
1101 <div class="doc_text">
1103 <p>This directory contains utilities for working with LLVM source code, and some
1104 of the utilities are actually required as part of the build process because they
1105 are code generators for parts of LLVM infrastructure.</p>
1108 <dt><tt><b>Burg/</b></tt> <dd><tt>Burg</tt> is an instruction selector
1109 generator -- it builds trees on which it then performs pattern-matching to
1110 select instructions according to the patterns the user has specified. Burg
1111 is currently used in the Sparc V9 backend.<p>
1113 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1114 that finds differences between code that LLC generates and code that LLI
1115 generates. This is a useful tool if you are debugging one of them,
1116 assuming that the other generates correct output. For the full user
1117 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
1119 <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
1120 update your CVS tree, but produce a much cleaner and more organized output
1121 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
1122 together all the new and updated files and modified files in separate
1123 sections, so you can see at a glance what has changed. If you are at the
1124 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1125 preferred way of updating the tree.<p>
1127 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1128 syntax-highlighting files which will work with Emacs and XEmacs editors,
1129 providing syntax highlighting support for LLVM assembly files and TableGen
1130 description files. For information on how to use the syntax files, consult
1131 the <tt>README</tt> file in that directory.<p>
1133 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1134 and outputs all non-generated source files, which is useful if one wishes
1135 to do a lot of development across directories and does not want to
1136 individually find each file. One way to use it is to run, for example:
1137 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1140 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1141 files in the current directory and then compiles and links the tool that
1142 is the first argument. For example, assuming you are in the directory
1143 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1144 simply running <tt>makellvm llc</tt> will make a build of the current
1145 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1146 causing a re-linking of LLC.<p>
1148 <dt><tt><b>NightlyTest.pl</b></tt> and
1149 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1150 cron script to generate nightly status reports of the functionality of
1151 tools, and the results can be seen by following the appropriate link on
1152 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
1154 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1155 the tool used to generate register descriptions, instruction set
1156 descriptions, and even assemblers from common TableGen description
1159 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1160 syntax-highlighting files which will work with the VIM editor, providing
1161 syntax highlighting support for LLVM assembly files and TableGen
1162 description files. For information on how to use the syntax files, consult
1163 the <tt>README</tt> file in that directory.<p>
1169 <!-- *********************************************************************** -->
1170 <div class="doc_section">
1171 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1173 <!-- *********************************************************************** -->
1175 <div class="doc_text">
1178 <li>First, create a simple C file, name it 'hello.c':
1180 #include <stdio.h>
1182 printf("hello world\n");
1187 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1188 <p><tt>% llvmgcc hello.c -o hello</tt></p>
1190 <p>Note that you should have already built the tools and they have to be
1191 in your path, at least <tt>gccas</tt> and <tt>gccld</tt>.</p>
1193 <p>This will create two result files: <tt>hello</tt> and
1194 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1195 corresponds the the compiled program and the library facilities that it
1196 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1197 file with <tt>lli</tt>, making the result directly executable. Note that
1198 all LLVM optimizations are enabled by default, so there is no need for a
1199 "-O3" switch.</p></li>
1201 <li><p>Run the program. To make sure the program ran, execute one of the
1202 following commands:</p>
1204 <p><tt>% ./hello</tt></p>
1208 <p><tt>% lli hello.bc</tt></p></li>
1210 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1213 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1215 <li><p>Compile the program to native assembly using the LLC code
1218 <p><tt>% llc hello.bc -o hello.s</tt></p>
1220 <li><p>Assemble the native assembly language file into a program:</p>
1222 <p><b>Solaris:</b><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native</tt></p>
1223 <p><b>Others:</b><tt>% gcc hello.s -o hello.native</tt></p>
1225 <li><p>Execute the native code program:</p>
1227 <p><tt>% ./hello.native</tt></p></li>
1233 <!-- *********************************************************************** -->
1234 <div class="doc_section">
1235 <a name="problems">Common Problems</a>
1237 <!-- *********************************************************************** -->
1239 <div class="doc_text">
1241 <p>If you are having problems building or using LLVM, or if you have any other
1242 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1243 Asked Questions</a> page.</p>
1247 <!-- *********************************************************************** -->
1248 <div class="doc_section">
1249 <a name="links">Links</a>
1251 <!-- *********************************************************************** -->
1253 <div class="doc_text">
1255 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1256 some simple things... there are many more interesting and complicated things
1257 that you can do that aren't documented here (but we'll gladly accept a patch
1258 if you want to write something up!). For more information about LLVM, check
1262 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1263 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1264 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project
1265 that Uses LLVM</a></li>
1270 <!-- *********************************************************************** -->
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1279 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1280 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
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